1. Field of the Invention
The present invention relates to an inkjet printing apparatus that can detect, from among a group of ejection ports formed in a print head, an ejection port whereat the ejection process is being performed abnormally.
2. Description of the Related Art
To perform printing, an inkjet printing apparatus ejects ink droplets through ejection ports formed in a print head. In general, a plurality of these ink ejection ports are formed and arranged so ink is ejected through the ejection port formation face of a print head. Ejection port arrays are formed by the ejection ports are arranged in rows.
When an inkjet printing apparatus, equipped with a print head wherein ejection port arrays are arranged in this manner, has not been used for an extended period of time, ink in the periphery of the ejection ports may solidify and cause clogging. Therefore, ink ejection failures may occur at some of the ejection ports in the inkjet printing apparatus. If printing is performed without resolving ink ejection failures at some of the clogged ink ejection ports, there is a probability that white stripes will appear in those portions of a printed image that correspond to the positions of the ejection ports where ejection failures have occurred, and accordingly, this will degrade the quality of the image. In order to prevent the degradation of the quality of a printed image, when ejection failures have occurred among the ejection ports of a print head, all defective ejection ports must be detected. For when an ejection port where an ejection failure has occurred has been detected, action can be taken to eliminate the cause of the malfunction or to employ a supplementary procedure. For example, either a recovery operation for the detective ejection port is performed to recover the normal ejection of ink through the relevant ejection port, or, in place of the defective ink ejection port, another, normal ejection port is employed to perform the ejection of ink.
In Japanese Patent Laid-Open No. 2002-292843, an inkjet printing apparatus is disclosed wherein a sensor, employed to detect ejection ports where ejection failures have occurred, is so arranged that the trajectory of an ink droplet ejected through an ejection port is positioned between a light emitting portion and a light receiving portion of the sensor. In this inkjet printing apparatus, ink is ejected when light is emitted by the light emitting portion to the light receiving portion, and a change in the signal received by the light receiving portion is detected to identify an ejection port at which an ejection failure has occurred.
According to the inkjet printing apparatus disclosed in Japanese Patent Laid-Open No. 2002-292843, movement of the print head is continued until ejection ports at which the detection of ejection failures is performed are arranged at a location opposite a sensor that detects a defective ejection port. When the ejection ports for which the detection of ejection failures is to be performed are arranged at a position opposite that where the sensor is located, the ink ejection states of the individual ejection ports are examined. Therefore, a print head that is a comparatively large part must be accurately positioned at the location of the sensor used to detect the ink ejection states of the ejection ports.
Recently, an inkjet printing apparatus has been especially introduced that is compatible with the printing of a comparatively large printing medium. Such an inkjet printing apparatus also employs a comparatively large print head to perform printing, and the load imposed for moving the large print head is accordingly increased. Especially, for aligning target ejection ports with the sensor, a fine adjustment of the positioning of the print head is performed by reducing the speed of the print head so as not to cause a print head overrun due to a comparatively large load. Therefore, an extended period of time is required for the fine adjustment of the positioning of the print head, and in all likelihood, a protracted period of time will be required to detect the ink ejection state of each ejection port.